KR20090027665A - Exhaust emission purifying system for v-type eight-cylinder internal combustion engine - Google Patents

Abstract

Provided is a technique, which can suppress that a fuel added from a fuel adding valve sticks to an exhaust passage, and that the fuel weaves out of an exhaust emission purifying device. The fuel adding instant, at which the fuel is added from fuel adding valves (11, 12), is switched, according to a running condition, to the instant, at which the instantaneous exhaust emission flow rates in exhaust pipes (7, 8) are different. In the case of a running condition, under which the fuel may seriously stick to the exhaust pipes (7, 8), therefore, the fuel is added at the instant when the instantaneous exhaust emissions through the exhaust pipes (7, 8) are high, so that the fuel may be easily entrained by the exhaust emissions to the vicinities of exhaust emission purifying devices (9, 10), thereby to suppress the stick of the fuel to the exhaust pipes (7, 8). In the case of a running condition, under which the fuel may seriously weave out of the exhaust emission purifying devices (9, 10), on the other hand, the fuel is added at the instant when the instantaneous exhaust emissions through the exhaust pipes (7, 8) are low, so that the fuel may be hardly entrained by the exhaust emissions and slowed down in its movement, thereby to suppress the weave of the fuel out of the exhaust emission purifying devices (9, 10).

Description

EXHAUST EMISSION PURIFYING SYSTEM FOR V-TYPE EIGHT-CYLINDER INTERNAL COMBUSTION ENGINE}

The present invention relates to an exhaust purification system for a V-type eight cylinder internal combustion engine.

Techniques have been known in which a NOx storage reduction catalyst (hereinafter referred to as a NOx catalyst) is provided in the exhaust passage of the internal combustion engine to purify the NOx of the exhaust gas of the internal combustion engine. Here, the NOx catalyst deteriorates as the amount of NOx occluded therein increases. Thus, in order to recover the performance of the NOx catalyst, the fuel is supplied to the NOx catalyst so that the NOx stored in the catalyst can be reduced and discharged (hereinafter referred to as "NOx reduction treatment"). In addition, SOx poisoning that lowers the performance of the NOx catalyst is generated by SOx of the exhaust gas stored in the NOx catalyst. To remove this SOx poisoning for performance recovery, fuel may sometimes be supplied to the NOx catalyst (hereinafter referred to as "SOx poisoning recovery treatment").

In addition, a technique is also known in which a filter is provided in the exhaust passage of the internal combustion engine to collect particulate matter (PM) of the exhaust gas of the internal combustion engine. In such a filter, as the accumulated amount of particulate matter trapped or collected increases, the back pressure of the exhaust gas is increased due to the clogging of the filter, thereby lowering engine performance. Thus, in order to restore the performance of the filter, the fueled and trapped PM is oxidized and removed (hereinafter referred to as "PM regeneration treatment"), and the NOx reduction treatment, SOx poisoning recovery treatment, and PM regeneration treatment together are "performance." Recovery process ".

Here, a technique is known in which a fuel addition valve for adding fuel to an upstream side of the exhaust gas purification device is provided for performing performance recovery processing of the exhaust gas purification device such as the aforementioned NOx catalyst, the aforementioned filter, and the like. In this technique, Japanese Patent Application Laid-Open No. 2001-280125 discloses that a fuel addition valve is mounted in the exhaust port of the cylinder closest to the exhaust dust collecting ring of the exhaust manifold and farthest from the opening of the EGR tube, so that the fuel It is proposed to add this cylinder at the time of an open state. This configuration attempts to supply fuel to the vicinity of the exhaust gas purifier while preventing fuel added from the fuel addition valve from adhering to the exhaust manifold and / or flowing into the EGR tube.

Furthermore, Japanese Laid-Open Patent Publication No. 2002-106332 discloses that the supply amount of the reducing agent used in one NOx reduction treatment operation is calculated based on the load of the internal combustion engine, so that the calculated amount of the reducing agent is added in a plurality of periods, It is proposed that a number of additions of the reducing agent are made to the crank angle of the internal combustion engine, whereby the addition is carried out when the exhaust valve is opened. Thus, efficient addition of the reducing agent can be effected while reliably entraining the reducing agent in the exhaust gas stream.

SUMMARY OF THE INVENTION An object of the present invention is to prevent the adhesion of fuel added to an exhaust passage from a fuel addition valve in a V-type 8-cylinder exhaust gas purification system, while simultaneously allowing fuel to leak or pass through the exhaust gas purification device. It is to provide a technique to suppress.

In the present invention, the following structure is adopted. That is, in the exhaust gas purification system for V type 8 cylinder internal combustion engine,

An exhaust passage provided for each of the individual banks of the V-shaped eight-cylinder internal combustion engine, and collectively extending from the respective cylinder to the individual banks so that exhaust gas from the internal combustion engine passes therethrough,

Exhaust gas purifiers each disposed in the exhaust passage and each configured to include a catalyst having an oxidation function, and

A fuel addition valve, each of which is located in the exhaust passage on the upper side of the exhaust gas purification apparatus, for adding fuel to the exhaust gas passing through the exhaust passage when the performance of the exhaust gas purification apparatus is restored;

The exhaust gas purifying system for the V-shaped eight-cylinder internal combustion engine is characterized in that the fuel addition timing, which is when the fuel is added from the fuel addition valve, is changed in an instantaneous exhaust gas flow rate of the exhaust passage according to engine operating conditions.

The fuel addition timing in which the fuel is added from the fuel addition valve is configured such that the instantaneous exhaust gas flow rate of the exhaust passage is changed within different periods according to engine operating conditions. For example, when the fuel added from the fuel addition valve is likely to be attached to the exhaust passage by the engine operating conditions, the fuel addition timing is changed within a period in which the instantaneous exhaust gas flow rate is high. In addition, when the fuel added from the fuel addition valve is more likely to leak through the exhaust gas purification device due to the engine operating conditions, the fuel addition timing is changed to a period during which the instantaneous exhaust gas flow rate is low.

Here, the instantaneous exhaust gas flow rate of the exhaust passage means the exhaust gas flow rate in the exhaust passage for a minimum or limited period in which the flow rate is changed by the change of the open / closed state of the cylinder exhaust valve. In a V-type 8-cylinder internal combustion engine, a period in which both exhaust valves of the same bank are open, a period in which one exhaust valve of the same bank is open, and an exhaust valve of all cylinders in the same bank are There is a closed period of time, and the instantaneous exhaust gas flow rate of the exhaust passage varies according to one of these periods. Thus, the instantaneous exhaust gas flow rate of the exhaust passage is a flow rate that changes over time in one cycle of the V-shaped eight-cylinder internal combustion engine.

Thus, when the operating conditions are likely to be attached to the exhaust passage with the fuel added from the fuel addition valve, fuel is added from the fuel addition valve when the instantaneous exhaust gas flow rate in the exhaust passage is high. As a result, the fuel can be easily transported in the vicinity of the exhaust gas purifier while entraining the exhaust gas, whereby the fuel can be prevented from adhering to the exhaust passage.

In addition, when the operating conditions are more likely to leak through the exhaust gas purifier from the fuel addition valve, fuel is added from the fuel addition valve when the instantaneous exhaust gas flow rate in the exhaust passage is low. As a result, the fuel cannot easily accompany the exhaust gas so that the movement of the fuel is slowed down, whereby the fuel can be suppressed from leaking out through the exhaust gas purifying apparatus.

According to the increasing accumulation amount of the exhaust gas flow rate discharged during the predetermined cycle period, the fuel addition timing is preferably changed within a period during which the instantaneous exhaust gas flow rate of the exhaust passage becomes smaller.

Here, the accumulated amount of the exhaust gas flow rate discharged during the predetermined cycle period is, for example, the total exhaust gas flow rate during the predetermined cycle period such as 720 ° crank angle interval in which each one cycle of all the cylinders in the V-type 8-cylinder internal combustion engine is completed. Is an integrated amount of, and this value changes depending on the rotation speed of the engine and the like. When the engine rotation speed is low, the integration amount is small, and the probability that fuel added from the fuel adding valve is attached to the exhaust passage is high. On the other hand, when the engine rotation speed is high, the integration amount becomes large, and the possibility that fuel added from the fuel adding valve is leaked through the exhaust gas purifying device is increased.

Accordingly, as the accumulated amount of the exhaust gas flow rate discharged during the predetermined cycle period increases, the fuel is added from the fuel addition valve when the instantaneous exhaust gas flow rate of the exhaust passage decreases, whereby the fuel added from the fuel addition valve Can be suppressed from adhering to the exhaust passage, and at the same time, fuel can also be suppressed from leaking through the exhaust gas purifier.

As the temperature of the exhaust gas becomes higher, it is preferable that the fuel addition timing be changed within a period in which the instantaneous exhaust gas flow rate of the exhaust passage becomes smaller.

Here, when the temperature of the exhaust gas is low, the droplets of the fuel are large and therefore it is difficult to accompany the fuel to the exhaust gas, thus increasing the possibility that the fuel added from the fuel addition valves adheres to the exhaust passage. On the other hand, when the temperature of the exhaust gas is high, the droplet of the fuel will be small and it will be easy to accompany the fuel to the exhaust gas, so that the fuel added from the fuel adding valve will be more likely to leak through the exhaust gas purification device.

Accordingly, fuel is added from the fuel addition valve when the instantaneous exhaust gas flow rate of the exhaust passage becomes smaller as the temperature of the exhaust gas becomes higher, thereby suppressing the fuel added from the fuel addition valve from adhering to the exhaust passage. It is also possible to simultaneously suppress fuel leakage through the exhaust gas purification device.

The V-type 8-cylinder internal combustion engine can be burned continuously in two predetermined cylinders of the same bank at 90 ° crank angle intervals and also in any cylinder of the same bank at 180 ° crank angle intervals. It is preferred that the V-type 8-cylinder internal combustion engine is not used, and depending on the engine operating conditions, the fuel addition timing may be that both exhaust valves of the two cylinders of the same bank are opened when combustion is continuously performed at a crank angle interval of 90 °. Period in the opened state, the latter period in which the exhaust valve of one predetermined cylinder is opened, if the combustion is not performed at a crank angle interval of 90 ° before and after combustion is performed in a predetermined cylinder of the same bank, or in the same bank. Combustion is not carried out at intervals of crank angle of 90 ° before and after combustion is performed in a predetermined predetermined cylinder. One of the first half of the period when the exhaust valve of one predetermined cylinder is open, and one of the periods when the exhaust valves of all cylinders of the same bank are closed when no combustion is performed in any cylinder at a crank angle interval of 180 °. It is desirable to be changed into.

In this way, it is possible to change the instantaneous exhaust gas flow rate of the exhaust passage.

The V-type 8-cylinder internal combustion engine can be burned continuously in two predetermined cylinders of the same bank at 90 ° crank angle intervals and also in any cylinder of the same bank at 180 ° crank angle intervals. It is preferable that the V-type 8-cylinder internal combustion engine is not used, and when the integration amount is less than or equal to a predetermined first integration amount, the fuel addition timing is determined by two cylinders of the same bank when combustion is continuously performed at a crank angle interval of 90 °. When the exhaust valves are all changed within a period of the open state, and the accumulation amount is more than a predetermined second integration amount larger than the predetermined first integration amount, the fuel addition timing is in any cylinder at crank angle intervals of 180 °. If combustion is not carried out, the exhaust valves of all cylinders of the same bank are changed within a period of closed state, When the accumulation amount is larger than the predetermined first integration amount and smaller than the predetermined second integration amount, the fuel addition timing is combusted at crank angle intervals of 90 ° before and after combustion is performed in a predetermined cylinder of the same bank. If is not carried out, it is preferable that the predetermined one-cylinder exhaust valve is changed within a period of open state.

Accordingly, the fuel addition timing can be divided according to the instantaneous exhaust gas flow rate of the exhaust passage, and when the instantaneous exhaust gas flow rate of the exhaust passage is smaller as the accumulated amount of the exhaust gas flow rate discharged during the predetermined cycle period is increased. Fuel is added from the fuel addition valve. Therefore, the fuel added from the fuel addition valve can be prevented from adhering to the exhaust passage, and at the same time, the fuel leaking out through the exhaust gas purifying apparatus can also be suppressed.

When the integration amount is larger than the first predetermined integration amount and is less than or equal to a third predetermined integration amount between the first and second integration amounts, the fuel addition timing is such that the exhaust valve of the one cylinder is opened. Preferably, the fuel is changed within the latter period of the state, and when the accumulation amount is larger than the predetermined third integration amount and between the predetermined first integration amount and the second integration amount and smaller than the predetermined second integration amount, the fuel It is preferable that the addition timing is changed within the first half period of the state where the exhaust valve of the predetermined one cylinder is opened.

Accordingly, the fuel addition timing can be further finely divided according to the instantaneous exhaust gas flow rate of the exhaust passage, so that the instantaneous exhaust gas flow rate of the exhaust passage is increased according to the increase in the accumulated amount of the exhaust gas flow rate discharged during the predetermined cycle period. Fuel can be added from the fuel addition valve when small. Therefore, the fuel added from the fuel adding valve can be prevented from adhering to the exhaust passage, and at the same time, the fuel can also be suppressed from leaking through the exhaust gas purifying apparatus.

1 is a diagram showing a schematic configuration of an internal combustion engine having an exhaust system to which an exhaust gas purification system is applied.

2 is a view showing a valve opening pattern of the exhaust valve in each cylinder of the internal combustion engine.

3 is a view showing a change in the instantaneous exhaust gas flow rate.

4 is a diagram illustrating a map for determining a fuel addition timing according to the first embodiment of the present invention.

5 is a diagram illustrating a map for determining a fuel addition timing according to the second embodiment of the present invention.

6 is a view showing a change in the instantaneous exhaust gas flow rate.

In the following, reference is made to specific embodiments according to the invention.

<1st embodiment>

1 shows a schematic configuration of an internal combustion engine having an exhaust system according to an embodiment of the present invention. The internal combustion engine 1 shown in FIG. 1 is a V-type eight cylinder four cycle diesel engine.

The internal combustion engine 1 is configured such that two banks are provided, including a first bank 2 and a second bank 3. The first bank 2 is provided with first, third, fifth and seventh cylinders, and the second bank 3 is provided with second, fourth, sixth and eighth cylinders.

A first exhaust manifold 5 connected to the individual cylinder 4 of the first bank 2 is connected to the first bank 2. A second exhaust manifold 6 connected to the individual cylinder 4 of the second bank 3 is connected to the second bank 3. The first exhaust manifold 5 and the second exhaust manifold 6 respectively collect or join the branch pipe portion connected to the individual cylinder 4 and the exhaust gas introduced from the branch pipe portion and flow it downstream. It has a dust collecting ring to send.

The exhaust pipe 7 is connected to the downstream side of the dust collecting ring of the first exhaust manifold 5. In addition, the exhaust pipe 8 is connected to the downstream side of the dust collecting ring of the second exhaust manifold 6. The exhaust pipes 7, 8 are connected to mufflers not shown at their distal ends. Here, the dust collecting rings and the exhaust pipes 7 and 8 of the first and second exhaust manifolds 5 and 6 correspond to the exhaust passage of the present invention.

In the middle of the exhaust pipe 7, an exhaust gas purification device 9 for purifying particulate matter and NOx of exhaust gas is disposed. In the middle of the exhaust pipe 8, an exhaust gas purification device 10 for purifying particulate matter and NOx of exhaust gas is disposed. The exhaust gas purifiers 9 and 10 each have a storage reduction type NOx catalyst having an oxidation function supported or supported by a wall flow tpe filter composed of a porous substrate. Here, the exhaust gas purification devices 9 and 10 correspond to the exhaust gas purification device of the present invention.

Here, the exhaust gas purification apparatuses 9 and 10 are not limited to the above-mentioned configuration, but for example, a filter without a storage reduction type NOx catalyst supported in this apparatus and a NOx storage reduction type disposed in series upstream of the filter. It may also consist of a catalyst.

A fuel addition valve 11 for adding fuel to the exhaust pipe 7 is disposed on the exhaust pipe 7 on the upstream side of the exhaust gas purification device 9. A fuel addition valve 12 for adding fuel to the exhaust pipe 8 is also arranged on the exhaust pipe 8 on the upstream side of the exhaust gas purifier 10. The fuel addition valves 11 and 12 are processes for restoring the performance of the exhaust gas purification apparatuses 9 and 10, such as NOx reduction treatment of the exhaust gas purification apparatuses 9 and 10, SOx poisoning recovery treatment, PM regeneration treatment, and the like. When adding fuel.

An electric control unit (ECU) 13 for controlling the internal combustion engine 1 is provided together with the internal combustion engine 1 of the above configuration. The ECU 13 controls the operation state of the internal combustion engine 1 and the like in accordance with the operating conditions of the internal combustion engine 1 and the driver's request, and in addition, a process for restoring the performance of the exhaust gas purification devices 9 and 10. To control.

Sensors such as the crank position sensor 14 and the like which are related to the operation state control of the internal combustion engine 1 are connected to the ECU 13 via electrical wiring, so that an output signal from such a sensor can be input to the ECU 13. On the other hand, a fuel injection valve or the like not shown in the internal combustion engine 1 is connected to the ECU 13 via electrical wiring, and in addition, the fuel addition valves 11 and 12 are also connected to the ECU 13 via electrical wiring. In connection, the components or elements can be controlled by the ECU 13.

In addition, the ECU 13 includes a CPU, a ROM, a RAM, and the like. The ROM stores programs for performing various kinds of control of the internal combustion engine 1, maps for storing related data, and the like. In addition to the routine of the NOx reduction process for reducing the NOx stored in the exhaust gas purification apparatuses 9 and 10, the routines of the SOx poisoning recovery process and the PM regeneration process are part of a program stored in the ROM of the ECU 13.

Next, the case where fuel is added from the fuel addition valves 11 and 12 in the process for the performance recovery of the exhaust gas purification apparatuses 9 and 10 of this embodiment is demonstrated. In carrying out the treatment for the performance recovery of the exhaust gas purification devices 9 and 10, fuel is added to the exhaust pipes 7 and 8 from the fuel addition valves 11 and 12 (hereinafter referred to as "fuel addition"). ).

However, at the time of fuel addition, if the integrated amount of exhaust gas flow rate discharged during one cycle of the internal combustion engine 1 (hereinafter referred to as integrated amount) is insufficient, the fuel added from the fuel addition valves 11 and 12 is exhaust gas. It may be attached to the exhaust pipes 7 and 8 without accompaniment. On the other hand, when the total amount is excessive, when the fuel added from the fuel addition valves 11 and 12 is excessively accompanied by the exhaust gas and leaks through or passes through the exhaust gas purification devices 9 and 10. There is.

Here, the accumulated amount of the exhaust gas flow rate discharged during one cycle of the internal combustion engine 1 is the integrated amount of the total exhaust gas flow rate in each range of 720 ° CA in which one cycle of the entire cylinder is completed in the V-type 8 cylinder diesel engine. This value changes depending on the rotational speed of the engine. The integrated amount decreases at low engine speed, but increases at high engine speed.

Here, in the V-type 8 cylinder diesel engine such as the internal combustion engine 1, the combustion order of the cylinders in each bank is set so that combustion does not occur in both banks simultaneously from the viewpoint of vibration prevention or the like. Thus, combustion of cylinders in one bank occurs at unequal intervals.

In FIG. 2, in each bank of a V-type 8 cylinder diesel engine such as the internal combustion engine 1, the valve-opening pattern of the exhaust valve of each cylinder is illustrated. In Fig. 2, the abscissa axis represents the crank angle, and the exhaust valves of the cylinders represented by each grid open at the crank angle at the left end of this grid. Further, the width of each grid is 90 ° CA, which does not mean that the valve opening timing of the exhaust valve of each cylinder is 90 ° CA, but merely represents the valve opening start time of the exhaust valve of each cylinder. Therefore, the valve opening timing of each exhaust valve is such that the exhaust valve of the cylinder represented by the grid is opened at the crank angle at the left end of the grid, and the exhaust valve of the cylinder is closed at a point in the subsequent third grid. In other words, the valve opening timing of the exhaust valve is 180 ° CA or more.

In this embodiment, the combustion in the first bank 2 is performed in the order of the first, the seventh, the third, and the fifth cylinder, and the combustion in the second bank 3 is performed in the second, fourth, The sixth and eighth cylinders are performed in this order. Thus, the order of the exhaust cycles is similar to that of the combustion cycles.

In addition, the valve opening pattern of the exhaust valve is as shown in FIG. 2, and in this embodiment, the flow rate of the instantaneous exhaust gas of the exhaust pipes 7 and 8 during the one cycle period of the internal combustion engine 1 (hereinafter, the instantaneous exhaust) Is called the gas flow rate).

Here, the instantaneous exhaust gas flow rate means an exhaust gas flow rate of the exhaust pipes 7 and 8 for an extremely small or limited time period in which the flow rate changes due to a change in the open / closed state of the cylinder exhaust valve. In a V 8-cylinder diesel engine, when the exhaust valve is open in two cylinders of the same bank, or when the exhaust valve is open in one cylinder of the same bank, or the exhaust valve is closed in all cylinders of the same bank. There is a time in the state, and the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 change according to one of these times. Accordingly, the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 can be said to be flow rates that change depending on the time elapsed during one cycle period of the V-type 8 cylinder diesel engine.

Here, in the present embodiment, the change in the flow rate of the exhaust gas at the moment of being discharged to the exhaust pipes 7 and 8 in each cylinder will be described based on FIG. 3. FIG. 3A shows the change in the instantaneous exhaust gas flow rate in the exhaust pipe 7, and FIG. 3B shows the change in the instantaneous exhaust gas flow rate in the exhaust pipe 8. In addition, in Fig. 3, the instantaneous exhaust gas flow rate indicated by the solid line represents the instantaneous exhaust gas flow rate of each cylinder, and the instantaneous exhaust gas flow rate shown by the broken line indicates that the exhaust valves of two cylinders of the same bank are open (that is, overlapped ( The total instantaneous exhaust gas flow rate at the time of overlapped state.

In the seventh, third cylinders of the first bank 2 and the sixth, eighth cylinders of the second bank 3, combustion is continuously performed in the range of 90 ° CA. Therefore, as shown in the period (A) of FIG. 3, the periods in which the exhaust valves of the two cylinders are both open overlap each other. In the period in which the two-cylinder exhaust valves are both in the open state overlapping each other (period A), the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 by the confluence of the exhaust gases discharged from these two cylinders join. Increases as indicated by dashed lines. As a result, the maximum instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are formed in a period (period A) in which both cylinder exhaust valves are in an open state.

In addition, in the first and fifth cylinders of each first bank 2 and the second and fourth cylinders of the second bank 3, an interval of 90 ° CA or more before and after combustion has occurred in one of these cylinders. In other cylinders no combustion is carried out. When combustion is carried out in one cylinder, the exhaust valve of one cylinder is in an open state, and when the exhaust valve of one cylinder is in an open state, the instantaneous exhaust gas flow rate is discharged from that cylinder and the exhaust pipe (7 or 8) is the instantaneous exhaust gas flow rate.

Here, the instantaneous exhaust gas flow rate discharged from the one cylinder is different from the first or first period in which the exhaust valve of one cylinder is in the open state and the second or second period in which the exhaust valve of the one cylinder is in the open state. . That is, as shown in FIG. 3, the instantaneous exhaust gas flow rate in the latter half period (period B) in which the exhaust valve is in the open state is greater than the instantaneous exhaust gas flow rate in the first half period (period C) in which the exhaust valve is in the open state.

As a result, the second largest instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are formed in the latter period (period B) in which one cylinder exhaust valve is in an open state. In addition, the third largest instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is formed in the first period (period C) in which the exhaust valve is in an open state.

Further, combustion is performed in the range of 180 ° CA between the combustion of the fifth cylinder and the first cylinder of the first bank 2 and the combustion of the second cylinder of the second bank 3 and the combustion of the fourth cylinder. Is not performed. As shown in FIG. 3, when combustion does not occur in the range of 180 ° CA, a period (period D) in which the exhaust valve is closed in all cylinders of one bank occurs. In this period in which the exhaust valves of all cylinders in one bank are closed, the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 become minimum. As a result, the minimum instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are formed in a period (period D) in which the exhaust valves of all cylinders in one bank are closed.

As described above, in the V type 8 cylinder diesel engine such as the internal combustion engine 1, the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 vary during one cycle period of the internal combustion engine 1. Therefore, in this embodiment, in view of the above-mentioned change of the exhaust gas flow rate, the fuel added from the fuel addition valves 11 and 12 is suppressed from adhering to the exhaust pipes 7 and 8, and the fuel is exhausted. In order to suppress leakage or passage through the gas purifier 9, 10, in accordance with the above-mentioned integration amount, the fuel addition timing is changed, and thus the instantaneous exhaust gas flow rate of the exhaust pipes 7, 8 is Will be different. Here, in this embodiment, the integrated amount becomes one parameter of the engine operating condition for changing the fuel addition timing.

That is, in this embodiment, the fuel addition timing is one of the four periods (period A to period D) described above, so that the fuel addition can be performed at a time when the instantaneous exhaust gas flow rate is optimized for the integrated amount. Is changed to

Specifically, as shown in Fig. 4, the fuel addition timing is changed within one of four periods (periods A to D) in which the instantaneous exhaust gas flow rate becomes smaller as the integrated amount increases. 4 is a map in which the integrated amount is shown on the abscissa axis.

For example, when the engine rotation speed is in the low speed range, the integration amount is the smallest. In this case, fuel addition is performed when the exhaust valves are both open in the two cylinders in which the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are greatest during the period A.

When the engine speed is in the low-medium speed range, the integration amount is secondly small. In this case, fuel addition is performed in the latter period in which the exhaust valve is in the open state in one cylinder where the instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is the second largest during the period (B).

When the engine speed is in the medium to high speed range, the integration amount is the third smallest. In this case, fuel addition is performed in the first half period in which the exhaust valve is in the open state in one cylinder where the instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is the third largest during the period C.

When the engine rotation speed is in the high speed range, the integration amount is the largest. In this case, fuel addition is executed when the exhaust valves are all closed in all cylinders of the bank in which the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are the smallest during the period D.

Here, as shown in FIG. 4, the integration amount at the boundary dividing the fuel addition timing into the period (A) and the period (B) is the first predetermined integration amount of the present invention, and the fuel addition timing is defined by the period (C) and the like. The integration amount at the boundary divided by the period (D) is the second predetermined integration amount of the present invention, and the integration amount at the boundary at which the fuel addition time is divided into the period (B) and the period (C) is determined by the predetermined agent of the present invention. 3 integration.

As described above, when the fuel added from the fuel addition valves 11 and 12 is not likely to accumulate in an integrated amount in which the possibility that the fuel added from the fuel addition valves 11 and 12 is attached to the exhaust pipes 7 and 8 is not sufficient, Is added in a period such as a period A and the like where the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are large. As a result, the fuel can be easily carried in the vicinity of the exhaust gas purification apparatuses 9 and 10 while accommodating the exhaust gas, whereby the fuel can be prevented from adhering to the exhaust pipes 7 and 8.

In addition, in the case where the cumulative amount of the fuel that is added from the fuel addition valves 11 and 12 is likely to leak or pass through the exhaust gas purification devices 9 and 10, the fuel is exhaust pipes 7 and 8. Instantaneous exhaust gas flow rate is added in a period such as a small period (D) or the like. As a result, the fuel cannot easily accompany the exhaust gas so that the movement of the fuel is slowed down, whereby the fuel can be suppressed from leaking out of the exhaust gas purifying devices 9 and 10.

<2nd embodiment>

In the first embodiment, by using the integrated amount as a parameter of the engine operating conditions, the fuel addition timing has been changed within a period in which the instantaneous exhaust gas flow rates are different from each other in accordance with this integrated amount. In the second embodiment, by using the exhaust gas temperature as a parameter of the engine operating condition in addition to this integration amount, the fuel addition timing is also changed within a period in which the instantaneous exhaust gas flow rates are different from each other according to this exhaust gas temperature. Here, the description of those similar to the components or parts of the first embodiment will be omitted.

When the temperature of the exhaust gas is low, the fuel droplets become large and therefore it is difficult to entrain the fuel to the exhaust gas, so that the fuel added from the fuel addition valves 11 and 12 is attached to the exhaust pipes 7 and 8. The chances are high. On the other hand, when the temperature of the exhaust gas is high, the fuel droplets become small and it is easy to accompany the fuel to the exhaust gas, so that the fuel added from the fuel addition valves 11 and 12 is exhaust gas purifier 9, 10) It is more likely to leak through.

Therefore, in this embodiment, in view of the change of the instantaneous exhaust gas flow rate described in the first embodiment and the temperature change of the exhaust gas shown above, the fuel added from the fuel addition valves 11 and 12 is attached to the exhaust passage. In order to suppress this, and at the same time to suppress the fuel leaking out or passing through the exhaust gas purification device, the fuel addition timing is changed within a different period of time according to the integration amount and the exhaust gas temperature.

That is, the fuel addition timing is one of the four periods (period (A) to period (D)) mentioned above so that the fuel addition can be performed at a time when the instantaneous exhaust gas flow rate is optimal for the integration amount and the temperature of the exhaust gas. Is changed.

Specifically, as shown in FIG. 5, the fuel addition timing is divided into four periods (period (A) to period (D) with the increase in the amount of integration and the decrease in the instantaneous exhaust gas flow rate as the temperature of the exhaust gas increases). ) Here, FIG. 5 is a map in which the accumulated amount appears on the abscissa axis and the temperature of the exhaust gas is shown on the ordinate axis.

For example, when the engine rotation speed is in the low speed range, the integrated amount is the smallest, and at the same time, when the engine load is below the intermediate load, the temperature of the exhaust gas becomes low. In this case, fuel addition is performed when the exhaust valves of the two cylinders having the largest instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 during the period A are both open.

When the engine rotation speed is in the low speed range, the integrated amount is the smallest, and at the same time, when the engine load is equal to or more than the intermediate load, the temperature of the exhaust gas becomes a high temperature. In this case, fuel addition is carried out in the latter period during which the one-cylinder exhaust valve of the second largest instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is opened during the period (B).

When the engine rotational speed is in the low-medium speed range, the integration amount becomes second small, and at the same time, when the engine load is in the low load range, the temperature of the exhaust gas becomes low. In this case, fuel addition is executed when the exhaust valves of the two cylinders with the largest instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 during the period A are open.

When the engine rotational speed is in the low-medium speed range, the integration amount becomes second small, and at the same time, when the engine load is in the medium-high load range, the temperature of the exhaust gas becomes high. In this case, fuel addition is carried out in the latter period during which the one-cylinder exhaust valve of the second largest instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is opened during the period (B).

When the engine rotational speed is in the medium-high speed range, the integration amount is thirdly reduced, and at the same time, when the engine load is in the low load range, the temperature of the exhaust gas becomes low. In this case, fuel addition is carried out in the latter period during which the one-cylinder exhaust valve of the second largest instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is opened during the period (B).

When the engine rotational speed is in the medium-high speed range, the integration amount is the third smallest, and at the same time, when the engine load is in the medium-high load range, the temperature of the exhaust gas becomes high temperature. In this case, fuel addition is carried out in the first half of the period in which the one-cylinder exhaust valve with the third largest instantaneous exhaust gas flow rate in the exhaust pipes 7 and 8 is opened during the period (C).

When the engine rotational speed is in the high speed range, the integrated amount is the largest, and at the same time, when the engine load is in the low load range, the temperature of the exhaust gas becomes low. In this case, fuel addition is carried out in the first half period in which the one-cylinder exhaust valve with the third largest instantaneous exhaust gas flow rate of the exhaust pipes 7 and 8 is opened during the period C.

When the engine rotational speed is in the high speed range, the integration amount is greatest, and at the same time, when the engine load is in the medium-high load range, the temperature of the exhaust gas becomes high temperature. In this case, fuel addition is performed in the period in which the exhaust valves of all the cylinders in one of the banks in which the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are smallest for the period D are closed.

As described above, when the fuel added from the fuel addition valves 11 and 12 is likely to be attached to the exhaust pipes 7 and 8 in an insufficient amount of integration or when the temperature of the exhaust gas is low, By changing the timing, fuel is added in a period such as a period A and the like where the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are large. As a result, the fuel can be easily transported in the vicinity of the exhaust gas purification apparatuses 9 and 10 while accompanying the exhaust gas, whereby the fuel can be prevented from adhering to the exhaust pipes 7 and 8.

In addition, when the fuel added from the fuel addition valves 11 and 12 is likely to leak or pass through the exhaust gas purification devices 9 and 10, or the cumulative amount is excessive or the temperature of the exhaust gas is high, Is added in a period such as a period D where the instantaneous exhaust gas flow rates of the exhaust pipes 7 and 8 are small. As a result, the fuel cannot easily accompany the exhaust gas, so that the movement of the fuel is slowed, whereby the fuel can be suppressed from leaking through the exhaust gas purification devices 9 and 10.

Although in the above-mentioned embodiment, the fuel addition timing is changed over the period (A) to period (D), the upper limit and the lower limit of the instantaneous exhaust gas flow rate at the time of fuel addition can also be set. For example, the relationship between the instantaneous exhaust gas flow rate for period (A)> the instantaneous exhaust gas flow rate for period (B)> the instantaneous exhaust gas flow rate for period (C)> the instantaneous exhaust gas flow rate for period (D) is satisfactorily satisfied. As shown in FIG. 6, the fuel addition timing is only in the period (A1) in the period (A), the period (B1) in the period (B), the period (C1) in the period (C), and the period (D). Is changed. According to this, the order or order of the instantaneous exhaust gas flow rates in each of the periods A1, B1, C1, D becomes clear, so that the fuel added from the fuel addition valves 11, 12 is exhaust pipes 7, 8 Can be suppressed in a more suitable way, and at the same time also in a more suitable way that fuel leaks out through the exhaust gas purification devices 9, 10.

Here, the exhaust gas purification system for V-shaped eight-cylinder internal combustion engine according to the present invention is not limited to the above-mentioned embodiment, and various changes and modifications can be made within the scope and spirit of the present invention.

According to the present invention, in the V-type 8-cylinder internal combustion engine exhaust gas purification system, adhesion of fuel added to the exhaust passage from the fuel addition valve can be suppressed, and at the same time, it is possible to suppress leakage or passage through the exhaust gas purification device. Can be.

Claims (6)

In the exhaust gas purification system for V type 8 cylinder internal combustion engine, An exhaust passage provided for each of the individual banks of the V-shaped eight-cylinder internal combustion engine, and collectively extending from the respective cylinder to the individual banks so that exhaust gas from the internal combustion engine passes therethrough, Exhaust gas purifiers each disposed in the exhaust passage and each configured to include a catalyst having an oxidation function, and A fuel addition valve, each of which is located in the exhaust passage on the upper side of the exhaust gas purification apparatus, for adding fuel to the exhaust gas passing through the exhaust passage when the performance of the exhaust gas purification apparatus is restored; The fuel addition timing at the time of adding fuel from the fuel addition valve is varied in instantaneous exhaust gas flow rate of the exhaust passage in accordance with engine operating conditions within a different period. The V type according to claim 1, wherein the fuel addition timing is changed within a period in which the instantaneous exhaust gas flow rate of the exhaust passage becomes smaller as the integration amount of the exhaust gas flow rate discharged during a predetermined cycle period increases. Exhaust gas purification system for 8-cylinder internal combustion engines. The V type 8 cylinder internal combustion according to claim 1 or 2, wherein the fuel addition timing is changed within a period in which the instantaneous exhaust gas flow rate of the exhaust passage becomes smaller as the temperature of the exhaust gas is increased. Engine exhaust purification system. The method according to any one of claims 1 to 3, The V-type 8-cylinder internal combustion engine can be burned continuously in two predetermined cylinders of the same bank at 90 ° crank angle intervals and also in any cylinder of the same bank at 180 ° crank angle intervals. V-type 8-cylinder internal combustion engine Depending on the engine operating conditions, the timing of the fuel addition is a predetermined cylinder of the same bank, in which the exhaust valves of both cylinders of the same bank are opened when combustion is continuously performed at a crank angle interval of 90 °. If combustion is not carried out at 90 ° crank angular intervals before or after combustion is carried out in the second half of the period when the exhaust valve of one predetermined cylinder is opened, before and after combustion is performed in a predetermined predetermined cylinder of the same bank. If combustion is not carried out at intervals of crank angle of °, the first half of the period when the exhaust valve of one predetermined cylinder is open, and of all cylinders of the same bank if combustion is not performed at any cylinder at crank angle intervals of 180 °. In a V-shaped 8 cylinder, characterized in that the exhaust valve is changed within one of the closed periods. Exhaust gas purification system for smoke pipes. The method of claim 2, The V-type 8-cylinder internal combustion engine can be burned continuously in two predetermined cylinders of the same bank at 90 ° crank angle intervals and also in any cylinder of the same bank at 180 ° crank angle intervals. V-type 8-cylinder internal combustion engine When the integration amount is less than or equal to the first predetermined integration amount, the fuel addition timing is changed within a period in which both cylinder exhaust valves of the same bank are opened when combustion is continuously performed at a crank angle interval of 90 °. , When the accumulation amount is equal to or greater than a predetermined second integration amount larger than the predetermined first integration amount, the fuel addition timing is exhausted of all cylinders of the same bank when no combustion is performed in any cylinder at a crank angle interval of 180 °. Change within a period of time when the valve is closed, When the accumulation amount is larger than the predetermined first integration amount and smaller than the predetermined second integration amount, the fuel addition timing is combusted at crank angle intervals of 90 ° before and after combustion is performed in a predetermined cylinder of the same bank. The exhaust gas purifying system for the V type 8 cylinder internal combustion engine, characterized in that when the operation is not performed, the exhaust valve of one predetermined cylinder is changed within a period of an open state. The method of claim 5, wherein When the cumulative amount is greater than the first predetermined amount and less than or equal to the third predetermined amount that is between the first and second predetermined amounts, the fuel addition timing is such that the exhaust valve of the predetermined cylinder is opened. Change within the second half of the state, When the accumulation amount is larger than the predetermined third integration amount that is between the predetermined first integration amount and the second integration amount and smaller than the predetermined second integration amount, the fuel addition timing is the exhaust valve of the predetermined one cylinder. Exhaust gas purification system for a V-shaped 8-cylinder internal combustion engine, characterized in that is changed within the first half of the open state.

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